Conventionally, nut runners are widely used as a tool for performing tightening work and loosening work of bolts & nuts and screws.
Nut runners are roughly classified as straight nut runners having an output shaft pivotally supported on a straight line against the rotating shaft of the drive source, and angle nut runners having an output shaft pivotally supported approximately perpendicular to the rotating shaft 1 of the drive source M. Angled nut runners are applied to tightening work and loosening work at comparatively narrow points where a straight nut runner cannot be used, as shown in FIG. 3.
As greater importance is attached to quality control of industrial products, in recent years, a production control system has been adopted which consists of automatically measuring-recording the number of tightened pieces and tightening force of bolts & nuts and screws, and feedback the results of measurement in real time to the production of industrial products.
In the angle nut runner indicated in FIG. 3, a torque transducer TM for performing measurement of tightening force is disposed at about the middle position of the nut runner body B, to be available for use for the above-described production control system.
However, in the case where the torque transducer TM for performing measurement of tightening force is disposed at about the middle position of the nut runner body B, there is a problem that the genuine tightening force cannot be measured accurately, because the tightening force measured by the torque transducer TM inevitably includes the resistance, etc. of the power transmission mechanism for transmitting the turning force of the drive source M to the output shaft 2, to be concrete, the bevel gear mechanism BG.